CO2 refrigeration system with integrated air conditioning module

ABSTRACT

An integrated CO 2  refrigeration and air conditioning (AC) system for use in a facility includes one or more CO 2  compressors configured to discharge a CO 2  refrigerant at a higher pressure for circulation through a circuit to provide cooling to one or more refrigeration loads in the facility and a receiver configured to receive the CO 2  refrigerant at a lower pressure through a high pressure valve. The integrated system further includes an AC module configured to deliver a chilled AC coolant to AC loads in the facility. The AC module includes an AC evaporator and an AC compressor. The AC evaporator has an inlet configured to receive CO 2  liquid and an outlet configured to discharge a CO 2  vapor. The AC compressor is arranged in parallel with the one or more CO 2  compressors and is configured to receive CO 2  vapor from both the AC evaporator and the receiver.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present Application claims the benefit of and priority to U.S.Provisional Application No. 61/646,082 filed May 11, 2012, U.S.Provisional Application No. 61/651,341 filed May 24, 2012, and U.S.Provisional Application No. 61/668,803 filed Jul. 6, 2012. U.S.Provisional Applications Nos. 61/646,082, 61/651,341, and 61/668,803 arehereby incorporated by reference in their entireties.

BACKGROUND

This section is intended to provide a background or context to theinvention recited in the claims. The description herein may includeconcepts that could be pursued, but are not necessarily ones that havebeen previously conceived or pursued. Therefore, unless otherwiseindicated herein, what is described in this section is not prior art tothe description and claims in this Application and is not admitted to beprior art by inclusion in this section.

The present disclosure relates generally to a refrigeration systemprimarily using carbon dioxide (i.e., CO₂) as a refrigerant. The presentdisclosure relates more particularly to a CO₂ refrigeration system forsupermarkets or like facilities, the refrigeration system having aflexible module that provides cooling for air conditioning (“AC”) loadsof the facility. The present disclosure relates more particularly to anAC module having an evaporator (e.g., an AC chiller, a fan-coil unit,etc.) to receive the CO₂ refrigerant and a compressor operating inparallel with compressors of the CO₂ refrigeration system.

Refrigeration systems that provide cooling to temperature controlleddisplay devices (e.g. cases, merchandisers, etc.) in supermarkets orsimilar facilities typically operate independently from air conditioningsystems used to cool the facilities during warm or humid weather (e.g.in warmer climates, during daily or seasonal temperature variations,etc.). Further, such refrigeration systems and air conditioning systemsare typically not integrated in a manner that increases the efficiencyof the system(s) or that provides flexible modularity in the way thatthe systems are integrated.

Accordingly, it would be desirable to provide a CO₂ refrigeration systemhaving a flexible module for integrating the cooling of air conditioningloads in a manner that increases the efficiency of the systems.

SUMMARY

One implementation of the present disclosure is an integrated CO₂refrigeration and air conditioning (AC) system for use in a facility.The integrated system includes one or more CO₂ compressors configured todischarge a CO₂ refrigerant at a higher pressure for circulation througha circuit to provide cooling to one or more refrigeration loads in thefacility and a receiver configured to receive the CO₂ refrigerant at alower pressure through a high pressure valve. The receiver has a CO₂liquid portion and a CO₂ vapor portion.

The integrated system further includes an AC module configured todeliver a chilled AC coolant to AC loads in the facility. The AC moduleincludes an AC evaporator and an AC compressor. The AC evaporator has aninlet configured to receive CO₂ liquid and an outlet configured todischarge a CO₂ vapor. The AC compressor is arranged in parallel withthe one or more CO₂ compressors and is configured to receive CO₂ vaporfrom both the AC evaporator and the receiver.

Another implementation of the present disclosure is another integratedCO2 refrigeration and air conditioning system for use in a facility. Theintegrated system includes a CO₂ refrigeration circuit configured tocirculate a CO₂ refrigerant to refrigeration loads in the facility andan AC module configured to deliver a chilled AC coolant to AC loads inthe facility.

The CO₂ refrigeration circuit includes a plurality of parallel CO₂compressors, a gas cooler/condenser, a receiver having a CO₂ vaporportion and a CO₂ liquid portion, and a CO₂ liquid supply line. The CO₂liquid supply line is coupled to the CO₂ liquid portion of the receiverand configured to direct CO₂ liquid to one or more refrigeration loadsin the facility.

The AC module includes an AC evaporator and an AC compressor. The ACevaporator has an inlet configured to receive the CO₂ refrigerant fromthe CO₂ refrigeration circuit and an outlet configured to discharge theCO₂ refrigerant. The AC compressor is arranged in parallel with theplurality of parallel CO₂ compressors, the AC compressor configured toreceive CO₂ vapor from both the AC evaporator and the receiver.

Another implementation of the present disclosure is yet anotherintegrated CO₂ refrigeration and air conditioning system for use in afacility. The integrated system includes a CO₂ refrigeration circuitconfigured to circulate a CO₂ refrigerant to refrigeration loads in thefacility and an AC module integrated with the CO₂ refrigeration circuitand configured to provide cooling for AC loads in the facility.

The CO₂ refrigeration circuit includes a CO₂ compressor configured todischarge the CO₂ refrigerant at a first pressure into a first fluidline and a receiver configured to receive the CO₂ refrigerant at asecond pressure lower than the first pressure. The receiver has a CO₂liquid portion and a CO₂ vapor portion. The CO₂ refrigeration circuitfurther includes a high pressure valve disposed between the CO₂compressor and the receiver. The high pressure valve is configured toreceive the CO₂ refrigerant at the first pressure from a second fluidline and discharge the CO₂ refrigerant to the second pressure.

The AC module includes an AC evaporator configured to receive CO₂refrigerant from a component of the CO₂ refrigeration circuit andtransfer heat to the CO₂ refrigerant. The component of the CO₂refrigeration circuit from which the CO₂ refrigerant is received isselected from a group consisting of: the second fluid line, the CO₂liquid portion of the receiver, and the high pressure valve. The ACmodule further includes an AC compressor arranged in parallel with theCO₂ compressor. The AC compressor is configured to receive vapor CO₂refrigerant from the CO₂ vapor portion of the receiver and to dischargevapor CO₂ refrigerant into the first fluid line.

Those skilled in the art will appreciate that the foregoing summary isillustrative only and is not intended to be in any way limiting. Otheraspects, inventive features, and advantages of the devices and/orprocesses described herein, as defined solely by the claims, will becomeapparent in the detailed description set forth herein and taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a CO₂ refrigeration systemhaving a low temperature (“LT”) system portion for cooling LT loads(e.g. LT evaporators in LT display devices) and a medium temperature(“MT”) system portion for cooling MT loads (e.g. MT evaporators in MTdisplay devices) in a facility such as a supermarket or the like,according to an exemplary embodiment.

FIG. 2 is a schematic representation of the CO₂ refrigeration system ofFIG. 1 having a flexible AC module for integrating cooling for airconditioning loads in the facility, according to an exemplaryembodiment.

FIG. 3 is a schematic representation of the CO₂ refrigeration system ofFIG. 1 having another flexible AC module for integrating cooling for airconditioning loads in the facility, according to another exemplaryembodiment.

FIG. 4 is a schematic representation of the CO₂ refrigeration system ofFIG. 1 having yet another flexible AC module for integrating cooling forair conditioning loads in the facility, according to another exemplaryembodiment.

DETAILED DESCRIPTION

Referring generally to the FIGURES, a CO₂ refrigeration system is shown,according to various exemplary embodiments. The CO₂ refrigeration systemmay be used to provide cooling for temperature controlled displaydevices in a supermarket or similar facility. Advantageously, the CO₂refrigeration system may include one or more flexible air conditioningmodules (i.e., “AC modules”) for integrating air conditioning loads(i.e., “AC loads”) or other loads associated with cooling the facility.The flexible AC modules may be desirable when the facility is located inwarmer climates, or locations having daily or seasonal temperaturevariations that make air conditioning desirable within the facility. Theflexible AC modules are “flexible” in the sense that they may have anyof a wide variety of capacities by varying the size, capacity, andnumber of heat exchangers and/or compressors provided within the ACmodules.

In some embodiments, the flexible AC modules are adapted to convenientlyinterconnect (e.g. “plug-and-play”) with the piping of an existing CO₂refrigeration system when integration is desirable for an intendedfacility or application. For example, the flexible AC modules may beintegrated with an existing CO₂ refrigeration system by forming only arelatively small number (e.g., 2-3) of connections between the flexibleAC modules and the CO₂ refrigeration system. To further increaseconvenience, the flexible AC modules may be connected with the existingCO₂ refrigeration system using quick-disconnects, flexiblehoses/connections, “plug-and-play” adapters, or other convenientconnection devices.

Advantageously, the AC modules may enhance or increase the efficiency ofthe systems (e.g., the CO₂ refrigeration system, the AC system, thecombined system, etc.) by the synergistic effects of combining thesource of cooling for both systems in a parallel compressionarrangement. In some embodiments, an AC compressor may be used to drawuncondensed CO₂ vapor from a receiving tank (e.g., a flash tank, the“receiver,” etc.) as a means for pressure control and regulation withinthe receiving tank. Using the AC compressor to effectuate pressurecontrol and regulation may provide a more efficient alternative to otherpressure regulation techniques such as bypassing CO₂ vapor through abypass valve to the lower pressure suction side of the CO₂ refrigerationsystem compressors.

Although the various embodiments of the disclosure are described interms of supermarket facilities, temperature controlled display devicesand air conditioning loads, other suitable loads for integration withina refrigeration system consistent with the principles described hereinare intended to be within the scope of this disclosure. Further,specific temperatures and/or pressures described herein are intended asillustrative only and are not intended to be limiting, as other pressureand/or temperature ranges may be used to suit other system variations orapplications.

Referring more particularly to FIG. 1, a CO₂ refrigeration system 100 isshown according to an exemplary embodiment. CO₂ refrigeration system 100may be a vapor compression refrigeration system which uses primarilycarbon dioxide as a refrigerant. CO₂ refrigeration system 100 and isshown to include a system of pipes, conduits, or other fluid channels(e.g., fluid conduits 1, 3, 5, 7, and 9) for transporting the carbondioxide between various thermodynamic components the refrigerationsystem. The thermodynamic components of CO₂ refrigeration system 100 areshown to include a gas cooler/condenser 2, a high pressure valve 4, areceiving tank 6, a gas bypass valve 8, a medium-temperature (“MT”)system portion 10, and a low-temperature (“LT”) system portion 20.

Gas cooler/condenser 2 may be a heat exchanger or other similar devicefor removing heat from the CO₂ refrigerant. Gas cooler/condenser 2 isshown receiving CO₂ vapor from fluid conduit 1. In some embodiments, theCO₂ vapor in fluid conduit 1 may have a pressure within a range fromapproximately 45 bar to approximately 100 bar (i.e., about 640 psig toabout 1420 psig), depending on ambient temperature and other operatingconditions. In some embodiments, gas cooler/condenser 2 may partially orfully condense CO₂ vapor into liquid CO₂ (e.g., if system operation isin a subcritical region). The condensation process may result in fullysaturated CO₂ liquid or a liquid-vapor mixture (e.g., having athermodynamic quality between 0 and 1). In other embodiments, gascooler/condenser 2 may cool the CO₂ vapor (e.g., by removing superheat)without condensing the CO₂ vapor into CO₂ liquid (e.g., if systemoperation is in a supercritical region). In some embodiments, thecooling/condensation process is an isobaric process. Gascooler/condenser 2 is shown outputting the cooled and/or condensed CO₂refrigerant into fluid conduit 3.

High pressure valve 4 receives the cooled and/or condensed CO₂refrigerant from fluid conduit 3 and outputs the CO₂ refrigerant tofluid conduit 5. High pressure valve 4 may control the pressure of theCO₂ refrigerant in gas cooler/condenser 2 by controlling an amount ofCO₂ refrigerant permitted to pass through high pressure valve 4. In someembodiments, high pressure valve 4 is a high pressure thermal expansionvalve (e.g., if the pressure in fluid conduit 3 is greater than thepressure in fluid conduit 5). In such embodiments, high pressure valve 4may allow the CO₂ refrigerant to expand to a lower pressure state. Theexpansion process may be an isenthalpic and/or adiabatic expansionprocess, resulting in a flash evaporation of the high pressure CO₂refrigerant to a lower pressure, lower temperature state. The expansionprocess may produce a liquid/vapor mixture (e.g., having a thermodynamicquality between 0 and 1). In some embodiments, the CO₂ refrigerantexpands to a pressure of approximately 38 bar (e.g., about 540 psig),which corresponds to a temperature of approximately 37° F. The CO₂refrigerant then flows from fluid conduit 5 into receiving tank 6.

Receiving tank 6 collects the CO₂ refrigerant from fluid conduit 5. Insome embodiments, receiving tank 6 may be a flash tank or other fluidreservoir. Receiving tank 6 includes a CO2 liquid portion and a CO2vapor portion and may contain a partially saturated mixture of CO₂liquid and CO₂ vapor. In some embodiments, receiving tank 6 separatesthe CO₂ liquid from the CO₂ vapor. The CO₂ liquid may exit receivingtank 6 through fluid conduits 9. Fluid conduits 9 may be liquid headersleading to either MT system portion 10 or LT system portion 20. The CO₂vapor may exit receiving tank 6 through fluid conduit 7. Fluid conduit 7is shown leading the CO₂ vapor to gas bypass valve 8.

Gas bypass valve 8 is shown receiving the CO₂ vapor from fluid conduit 7and outputting the CO₂ refrigerant to MT system portion 10. In someembodiments, gas bypass valve 8 regulates or controls the pressurewithin receiving tank 6 by controlling an amount of CO₂ refrigerantpermitted to pass through gas bypass valve 8 (e.g., by regulating aposition of gas bypass valve 8). Gas bypass valve 8 may open and closeas needed to regulate the pressure within receiving tank 6. In someembodiments, gas bypass valve 8 may be a thermal expansion valve (e.g.,if the pressure on the downstream side of gas bypass valve 8 is lowerthan the pressure in fluid conduit 7). According to one embodiment, thepressure within receiving tank 6 is regulated by gas bypass valve 8 to apressure of approximately 38 bar, which corresponds to about 37° F.Advantageously, this pressure/temperature state (i.e., approximately 38bar, approximately 37° F.) may facilitate the use of coppertubing/piping for the downstream CO₂ lines of the system. Additionally,this pressure/temperature state may allow such copper tubing to operatein a substantially frost-free manner.

Still referring to FIG. 1, MT system portion 10 is shown to include oneor more expansion valves 11, one or more MT evaporators 12, and one ormore MT compressors 14. In various embodiments, any number of expansionvalves 11, MT evaporators 12, and MT compressors 14 may be present.Expansion valves 11 may be electronic expansion valves or other similarexpansion valves. Expansion valves 11 are shown receiving liquid CO₂refrigerant from fluid conduit 9 and outputting the CO₂ refrigerant toMT evaporators 12. Expansion valves 11 may cause the CO₂ refrigerant toundergo a rapid drop in pressure, thereby expanding the CO₂ refrigerantto a lower pressure, lower temperature state. In some embodiments,expansion valves 11 may expand the CO₂ refrigerant to a pressure ofapproximately 30 bar. The expansion process may be an isenthalpic and/oradiabatic expansion process.

MT evaporators 12 are shown receiving the cooled and expanded CO₂refrigerant from expansion valves 11. In some embodiments, MTevaporators may be associated with display cases/devices (e.g., if CO₂refrigeration system 100 is implemented in a supermarket setting). MTevaporators 12 may be configured to facilitate the transfer of heat fromthe display cases/devices into the CO₂ refrigerant. The added heat maycause the CO₂ refrigerant to evaporate partially or completely.According to one embodiment, the CO₂ refrigerant is fully evaporated inMT evaporators 12. In some embodiments, the evaporation process may bean isobaric process. MT evaporators 12 are shown outputting the CO₂refrigerant via fluid conduits 13, leading to MT compressors 14.

MT compressors 14 compress the CO₂ refrigerant into a superheated vaporhaving a pressure within a range of approximately 45 bar toapproximately 100 bar. The output pressure from MT compressors 14 mayvary depending on ambient temperature and other operating conditions. Insome embodiments, MT compressors 14 operate in a transcritical mode. Inoperation, the CO₂ discharge gas exits MT compressors 14 and flowsthrough fluid conduit 1 into gas cooler/condenser 2.

Still referring to FIG. 1, LT system portion 20 is shown to include oneor more expansion valves 21, one or more LT evaporators 22, and one ormore LT compressors 24. In various embodiments, any number of expansionvalves 21, LT evaporators 22, and LT compressors 24 may be present. Insome embodiments, LT system portion 20 may be omitted and the CO₂refrigeration system 100 may operate with an AC module interfacing withonly MT system 10.

Expansion valves 21 may be electronic expansion valves or other similarexpansion valves. Expansion valves 21 are shown receiving liquid CO₂refrigerant from fluid conduit 9 and outputting the CO₂ refrigerant toLT evaporators 22. Expansion valves 21 may cause the CO₂ refrigerant toundergo a rapid drop in pressure, thereby expanding the CO₂ refrigerantto a lower pressure, lower temperature state. The expansion process maybe an isenthalpic and/or adiabatic expansion process. In someembodiments, expansion valves 21 may expand the CO₂ refrigerant to alower pressure than expansion valves 11, thereby resulting in a lowertemperature CO₂ refrigerant. Accordingly, LT system portion 20 may beused in conjunction with a freezer system or other lower temperaturedisplay cases.

LT evaporators 22 are shown receiving the cooled and expanded CO₂refrigerant from expansion valves 21. In some embodiments, LTevaporators may be associated with display cases/devices (e.g., if CO₂refrigeration system 100 is implemented in a supermarket setting). LTevaporators 22 may be configured to facilitate the transfer of heat fromthe display cases/devices into the CO₂ refrigerant. The added heat maycause the CO₂ refrigerant to evaporate partially or completely. In someembodiments, the evaporation process may be an isobaric process. LTevaporators 22 are shown outputting the CO₂ refrigerant via fluidconduit 23, leading to LT compressors 24.

LT compressors 24 compress the CO₂ refrigerant. In some embodiments, LTcompressors 24 may compress the CO₂ refrigerant to a pressure ofapproximately 30 bar (e.g., about 425 psig) having a saturationtemperature of approximately 23° F. (e.g., about −5° C.). LT compressors24 are shown outputting the CO₂ refrigerant through fluid conduit 25.Fluid conduit 25 may be fluidly connected with the suction (e.g.,upstream) side of MT compressors 14.

In some embodiments, the CO₂ vapor that is bypassed through gas bypassvalve 8 is mixed with the CO₂ refrigerant gas exiting MT evaporators 12(e.g., via fluid conduit 13). The bypassed CO₂ vapor may also mix withthe discharge CO₂ refrigerant gas exiting LT compressors 24 (e.g., viafluid conduit 25). The combined CO₂ refrigerant gas may be provided tothe suction side of MT compressors 14.

Referring now to FIG. 2, a flexible AC module 30 for integrating ACcooling loads in a facility with CO₂ refrigeration system 100 is shown,according to an exemplary embodiment. AC module 30 is shown to includean AC evaporator 32 (e.g., a liquid chiller, a fan-coil unit, a heatexchanger, etc.), an expansion device 34 (e.g. an electronic expansionvalve), and at least one AC compressor 36. In some embodiments, flexibleAC module 30 further includes a suction line heat exchanger 37 and CO₂liquid accumulator 39. The size and capacity of the AC module 30 may bevaried to suit any intended load or application by varying the numberand/or size of evaporators, heat exchangers, and/or compressors withinAC module 30.

Advantageously, AC module 30 may be readily connectible to CO₂refrigeration system 100 using a relatively small number (e.g., aminimum number) of connection points. According to an exemplaryembodiment, AC module 30 may be connected to CO₂ refrigeration system100 at three connection points: a high-pressure liquid CO₂ lineconnection 38, a lower-pressure CO₂ vapor line (gas bypass) connection40, and a CO₂ discharge line 42 (to gas cooler/condenser 2). Each ofconnections 38, 40 and 42 may be readily facilitated using flexiblehoses, quick disconnect fittings, highly compatible valves, and/or otherconvenient “plug-and-play” hardware components. In some embodiments,some or all of connections 38, 40, and 42 may be arranged to takeadvantage of the pressure differential between gas cooler/condenser 2and receiving tank 6.

Still referring to FIG. 2, when AC module 30 is installed in CO₂refrigeration system 100, AC compressor 36 may operate in parallel withMT compressors 14. For example, a portion of the high pressure CO₂refrigerant discharged from gas cooler/condenser 2 (e.g., into fluidconduit 3) may be directed through CO₂ liquid line connection 38 andthrough expansion device 34. Expansion device 34 may allow the highpressure CO₂ refrigerant to expand a lower pressure, lower temperaturestate. The expansion process may be an isenthalpic and/or adiabaticexpansion process. The expanded CO₂ refrigerant may then be directedinto AC evaporator 32. In some embodiments, expansion device 34 adjuststhe amount of CO₂ provided to AC evaporator 32 to maintain a desiredsuperheat temperature at (or near) the outlet of the AC evaporator 32.After passing through AC evaporator 32, the CO₂ refrigerant may bedirected through suction line heat exchanger 37 and CO₂ liquidaccumulator 39 to the suction (i.e., upstream) side of AC compressor 36.

In some embodiments, AC evaporator 32 acts as a chiller to provide asource of cooling (e.g., building zone cooling, ambient air cooling,etc.) for the facility in which CO₂ refrigeration system 100 isimplemented. In some embodiments, AC evaporator 32 absorbs heat from anAC coolant that circulates to the AC loads in the facility. In otherembodiments, AC evaporator 32 may be used to provide cooling directly toair in the facility.

According to an exemplary embodiment, AC evaporator 32 is operated tomaintain a CO₂ refrigerant temperature of approximately 37° F. (e.g.,corresponding to a pressure of approximately 38 bar). AC evaporator 32may maintain this temperature and/or pressure at an inlet of ACevaporator 32, an outlet of AC evaporator 32, or at another locationwithin AC module 30. In other embodiments, expansion device 34 maymaintain a desired CO₂ refrigerant temperature. The CO₂ refrigeranttemperature maintained by AC evaporator 32 or expansion device 34 (e.g.,approximately 37° F.) may be well-suited in most applications forchilling an AC coolant supply (e.g. water, water/glycol, or other ACcoolant which expels heat to the CO₂ refrigerant). The AC coolant may bechilled to a temperature of about 45° F. or other temperature desirablefor AC cooling applications in many types of facilities.

Advantageously, integrating AC module 30 with CO₂ refrigeration system100 may increase the efficiency of CO₂ refrigeration system 100. Forexample, during warmer periods (e.g. summer months, mid-day, etc.) theCO₂ refrigerant pressure within gas cooler/condenser 2 tends toincrease. Such warmer periods may also result in a higher AC coolingload required to cool the facility. By integrating AC module 30 withrefrigeration system 100, the additional CO₂ capacity (e.g., the higherpressure in gas cooler/condenser 2) may be used advantageously toprovide cooling for the facility. The dual effects of warmerenvironmental temperatures (e.g., higher CO₂ refrigerant pressure and anincreased cooling load requirement) may both be addressed and resolvedin an efficient and synergistic manner by integrating AC module 30 withCO₂ refrigeration system 100.

Additionally, according to the embodiment illustrated in FIG. 2, ACmodule 30 can be used to more efficiently regulate the CO₂ pressure inreceiving tank 6. Such pressure regulation may be accomplished bydrawing CO₂ vapor directly from the receiving tank 6 and avoiding (orminimizing) the need to bypass CO₂ vapor from the receiving tank 6 tothe lower-pressure suction side of the MT compressors 14 (e.g., throughgas bypass valve 8).

For example, in system configurations without AC module 30, gas bypassvalve 8 operates (e.g. modulates) to bypass an amount of CO₂ vapor fromreceiving tank 6 to the suction side of MT compressors 14 as necessaryto maintain or regulate the CO₂ refrigerant pressure within receivingtank 6. The CO₂ refrigerant pressure may drop when passing through gasbypass valve 8 (e.g., from approximately 38 bar (about 540 psig) toapproximately 30 bar (about 425 psig)). Any CO₂ vapor bypassed fromreceiving tank 6 to the suction side of MT compressors 14 (e.g., throughgas bypass valve 8) is necessarily re-compressed from the lower pressureof about 30 bar by the MT compressors 14.

Advantageously, when AC module 30 is integrated with CO₂ refrigerationsystem 100, CO₂ vapor from receiving tank 6 is provided through CO₂vapor line connection 40 to the downstream side of AC evaporator 32 andthe suction side of AC compressor 36. Such integration may establish analternate (or supplemental) path for bypassing CO₂ vapor from receivingtank 6, as may be necessary to maintain the desired pressure (e.g.,approximately 38 bar) within receiving tank 6. In some embodiments, ACmodule 30 draws its supply of CO₂ refrigerant from line 38, therebyreducing the amount of CO₂ that is received within receiving tank 6. Inthe event that the pressure in receiving tank 6 increases above thedesired pressure (e.g. 38 bar, etc.), CO₂ vapor can be drawn by ACcompressor 36 through CO₂ vapor line 40 in an amount sufficient tomaintain the desired pressure within receiving tank 6. The ability touse the CO₂ vapor line 40 and AC compressor 36 as a supplemental bypasspath for CO₂ vapor from receiving tank 6 provides a more efficient wayto maintain the desired pressure in receiving tank 6 and avoids orminimizes the need to directly bypass CO₂ vapor across gas bypass valve8 to the lower-pressure suction side of the MT compressors 14.

Still referring to FIG. 2, at intersection 41, the CO₂ vapor dischargedfrom AC evaporator 32 may be mixed with CO₂ vapor output from receivingtank 6 (e.g., through fluid conduit 7 and vapor line 40, as necessaryfor pressure regulation). The mixed CO₂ vapor may then be directedthrough suction line heat exchanger 37 and liquid CO₂ accumulator 39 tothe suction (e.g., upstream) side of AC compressor 36. AC compressor 36compresses the mixed CO₂ vapor and discharges the compressed CO₂refrigerant into connection line 42. Connection line 42 may be fluidlyconnected to fluid conduit 1, thereby forming a common discharge headerwith MT compressors 14. The common discharge header is shown leading togas cooler/condenser 2 to complete the cycle.

Suction line heat exchanger 37 may be used to transfer heat from thehigh pressure CO₂ refrigerant exiting gas cooler/condenser 2 (e.g., viafluid conduit 3) to the mixed CO₂ refrigerant at or near intersection41. Suction line heat exchanger 37 may help cool/sub-cool the highpressure CO₂ refrigerant in fluid conduit 3. Suction line heat exchanger37 may also assist in ensuring that the CO₂ refrigerant approaching thesuction of AC compressor 36 is sufficiently superheated (e.g., having asuperheat or temperature exceeding a threshold value) to preventcondensation or liquid formation on the upstream side of AC compressor36. In some embodiments, CO₂ liquid accumulator 39 may also be includedto further prevent any CO₂ liquid from entering AC compressor 36.

Still referring to FIG. 2, AC module 30 may be integrated with CO₂refrigeration system 100 such that integrated system can adapt to a lossof AC compressor 36 (e.g. due to equipment malfunction, maintenance,etc.), while still maintaining cooling for the AC loads and stillproviding CO₂ pressure control for receiving tank 6. For example, in theevent that AC compressor 36 becomes non-functional, the CO₂ vapordischarged from AC evaporator 32 may be automatically (i.e. upon loss ofsuction from the AC compressor) directed back through CO₂ vapor lineconnection 40 toward fluid conduit 7. As the CO₂ refrigerant pressureincreases in receiving tank 6 above the desired setpoint (e.g. 38 bar),the CO₂ vapor can be bypassed through gas bypass valve 8 and compressedby MT compressors 14. The parallel compressor arrangement of ACcompressor 36 and MT compressors 14 allows for continued operation of ACmodule 30 in the event of an inoperable AC compressor 36.

Referring now to FIG. 3, a flexible AC module 130 for integrating ACcooling loads in a facility with CO₂ refrigeration system 100 is shown,according to another exemplary embodiment. AC Module 130 is shown toinclude an AC evaporator 132 (e.g., a liquid chiller, a fan-coil unit, aheat exchanger, etc.), an expansion device 134 (e.g. an electronicexpansion valve), and at least one AC compressor 136. In someembodiments, flexible AC module 30 further includes a suction line heatexchanger 137 and CO₂ liquid accumulator 139. AC evaporator 132,expansion device 134, AC compressor 136, suction line heat exchanger137, and CO₂ liquid accumulator 139 may be the same or similar toanalogous components (e.g., AC evaporator 32, expansion device 34, ACcompressor 36, suction line heat exchanger 37, and CO₂ liquidaccumulator 39) of AC module 30. The size and capacity of AC module 130may be varied to suit any intended load or application (e.g., by varyingthe number and/or size of evaporators, heat exchangers, and/orcompressors within AC module 130.

In some embodiments, AC module 130 is readily connectible to CO₂refrigeration system 100 by a relatively small number (e.g., a minimumnumber) of connection points. According to an exemplary embodiment, ACmodule 130 may be connected to CO₂ refrigeration system 100 at threeconnection points: a liquid CO₂ line connection 138, a CO₂ vapor lineconnection 140, and a CO₂ discharge line 142. Liquid CO₂ line connection138 is shown connecting to fluid conduit 9 and may receive liquid CO₂refrigerant from receiving tank 6. CO₂ vapor line connection 140 isshown connecting to fluid conduit 7 and may receive CO₂ bypass gas fromreceiving tank 6. CO₂ discharge line 142 is shown connecting the output(e.g., downstream side) of AC compressor 136 to fluid conduit 1, leadingto gas cooler/condenser 2. Each of connections 138, 140 and 142 may bereadily facilitated using flexible hoses, quick disconnect fittings,highly compatible valves, and/or other convenient “plug-and-play”hardware components.

In operation, a portion of the liquid CO₂ refrigerant exiting receivingtank 6 (e.g., via fluid conduit 9) may be directed through CO₂ liquidline connection 138 and through expansion device 134. Expansion device34 may allow the liquid CO₂ refrigerant to expand a lower pressure,lower temperature state. The expansion process may be an isenthalpicand/or adiabatic expansion process. The expanded CO₂ refrigerant maythen be directed into AC evaporator 132. In some embodiments, expansiondevice 134 adjusts the amount of CO₂ provided to AC evaporator 132 tomaintain a desired superheat temperature at (or near) the outlet of theAC evaporator 132. After passing through AC evaporator 132, the CO₂refrigerant may be directed through suction line heat exchanger 137 andCO₂ liquid accumulator 139 to the suction (i.e., upstream) side of ACcompressor 136.

Still referring to FIG. 3, one primary difference between AC module 30and AC module 130 is that AC module 130, avoids the high pressure CO₂inlet (e.g., from fluid conduit 3) as a source of CO₂. Instead, ACmodule 130 uses a lower-pressure source of CO₂ refrigerant supply (e.g.,from fluid conduit 9). Fluid conduit 9 may be fluidly connected withreceiving tank 6 and may operate at a pressure equivalent orsubstantially equivalent to the pressure within receiving tank 6. Insome embodiments, fluid conduit 9 provides liquid CO₂ refrigerant havinga pressure of approximately 38 bar.

In some implementations, AC module 130 may be used as an alternative orsupplement to AC module 30. The configuration provided by AC module 130may be desirable for implementations in which AC evaporator 132 is notmounted on a refrigeration rack with the components of CO₂ refrigerationsystem 100. AC module 130 may be used for implementations in which ACevaporator 132 is located elsewhere in the facility (e.g. near the ACloads). Additionally, the lower pressure liquid CO₂ refrigerant providedto AC module 130 (e.g., from fluid conduit 9 rather than from fluidconduit 3) may facilitate the use of lower pressure components forrouting the CO₂ refrigerant (e.g. copper tubing/piping, etc.).

In some embodiments, AC module 130 may include a pressure-reducingdevice 135. Pressure reducing-device 135 may be a motor-operated valve,a manual expansion valve, an electronic expansion valve, or otherelement capable of effectuating a pressure reduction in a fluid flow.Pressure-reducing device 135 may be positioned in line with vapor lineconnection 140 (e.g., between fluid conduit 7 and intersection 141). Insome embodiments, pressure-reducing device 135 may reduce the pressureat the outlet of AC evaporator 132. In some embodiments, the heatabsorption process which occurs within AC evaporator 132 is asubstantially isobaric process. In other words, the CO₂ pressure at boththe inlet and outlet of AC evaporator 132 may be substantially equal.Additionally, the CO₂ vapor in fluid conduit 7 and the liquid CO₂ influid conduit 9 may have substantially the same pressure since bothfluid conduits 7 and 9 draw CO₂ refrigerant from receiving tank 6.Therefore, pressure-reducing device may provide a pressure dropsubstantially equivalent to the pressure drop caused by expansion device134.

In some embodiments, line connection 140 may be used as an alternate (orsupplemental) path for directing CO₂ vapor from receiving tank 6 to thesuction of AC compressor 136. Line connection 140 and AC compressor 136may provide a more efficient mechanism of controlling the pressure inreceiving tank 6 (e.g., rather than bypassing the CO₂ vapor to thesuction side of the MT compressors 14, as described with reference to ACmodule 30), thereby increasing the efficiency of CO₂ refrigerationsystem 100.

Referring now to FIG. 4, a flexible AC module 230 for integratingcooling loads in a facility with CO₂ refrigeration system 100 is shown,according to another exemplary embodiment. AC module 230 is shown toinclude an AC evaporator 232 (e.g., a liquid chiller, a fan-coil unit, aheat exchanger, etc.) and at least one AC compressor 236. In someembodiments, flexible AC module 30 further includes a suction line heatexchanger 237 and CO₂ liquid accumulator 239. AC evaporator 232, ACcompressor 236, suction line heat exchanger 237, and CO₂ liquidaccumulator 239 may be the same or similar to analogous components(e.g., AC evaporator 32, AC compressor 36, suction line heat exchanger37, and CO₂ liquid accumulator 39) of AC module 30. AC module 230 doesnot require an expansion device as previously described with referenceto AC modules 30 and 130 (e.g., expansion devices 34 and 134). The sizeand capacity of the AC module 230 may be varied to suit any intendedload or application by varying the number and/or size of evaporators,heat exchangers, and/or compressors within AC module 230.

Advantageously, AC module 230 may be readily connectible to CO₂refrigeration system 100 using a relatively small number (e.g., aminimum number) of connection points. According to an exemplaryembodiment, AC module 30 may be connected to CO₂ refrigeration system100 at two connection points: a CO₂ vapor line connection 240, and a CO₂discharge line 242. CO₂ vapor line connection 240 is shown connecting tofluid conduit 7 and may receive (if necessary) CO₂ bypass gas fromreceiving tank 6. CO₂ discharge line 242 is shown connecting the outputof AC compressor 236 to fluid conduit 1, which leads to gascooler/condenser 2. Both of connections 240 and 242 may be readilyfacilitated using flexible hoses, quick disconnect fittings, highlycompatible valves, and/or other convenient “plug-and-play” hardwarecomponents.

In some embodiments, AC module 230 has an inlet connection 244 and anoutlet connection 246. Both inlet connection 244 and outlet connection246 may connect (e.g., directly or indirectly) to respective inlet andoutlet ports of AC evaporator 232. AC evaporator 232 may be positionedin line with fluid conduit 5 between high pressure valve 4 and receivingtank 6. AC evaporator 232 is shown receiving an entire mass flow of athe CO₂ refrigerant from gas cooler/condenser 2 and high pressure valve4. AC evaporator 232 may receive the CO₂ refrigerant as a liquid-vapormixture from high pressure valve 4. In some embodiments, the CO₂liquid-vapor mixture is supplied to AC evaporator 232 at a temperatureof approximately 3° C. In other embodiments, the CO₂ liquid-vapormixture may have a different temperature (e.g., greater than 3° C., lessthan 3° C.) or a temperature within a range (e.g., including 3° C. ornot including 3° C.).

Within AC evaporator 232, a portion of the CO₂ liquid in the mixtureevaporates to chill a circulating AC coolant (e.g. water, water/glycol,or other AC coolant which expels heat to the CO₂ refrigerant). In someembodiments, the AC coolant may be chilled from approximately 12° C. toapproximately 7° C. In other embodiments, other temperatures ortemperature ranges may be used. The amount of CO₂ liquid whichevaporates may depend on the cooling load (e.g., rate of heat transfer,cooling required to achieve a setpoint, etc.). After chilling the ACcoolant, the entire mass flow of the CO₂ liquid-vapor mixture may exitAC evaporator 232 and AC module 230 (e.g., via outlet connection 246)and may be directed to receiving tank 6.

CO₂ refrigerant vapor in receiving tank 6 can exit receiving tank 6 viafluid conduit 7. Fluid conduit 7 is shown fluidly connected with thesuction side of AC compressor 236 (e.g., by vapor line connection 240).In some embodiments, CO₂ vapor from receiving tank 6 travels throughfluid conduit 7 and vapor line connection 240 and is compressed by ACcompressor 236. AC compressor 236 may be controlled to regulate thepressure of CO₂ refrigerant within receiving tank 6. This method ofpressure regulation may provide a more efficient alternative tobypassing the CO₂ vapor through gas bypass valve 8.

Advantageously, AC module 230 provides an AC evaporator that operates“in line” (e.g., in series, via a linear connection path, etc.) to useall of the CO₂ liquid-vapor mixture provided by high-pressure valve 4for cooling the AC loads. This cooling may evaporate some or all of theliquid in the CO₂ mixture. After exiting AC module 230, the CO₂refrigerant (now having an increased vapor content) is directed toreceiving tank 6. From receiving tank 6, the CO₂ refrigerant and mayreadily be drawn by AC compressor 236 to control and/or maintain adesired pressure in receiving tank 6.

According to any exemplary embodiment, an AC module (e.g., AC module 30,130, or 230) as described herein for use with CO₂ refrigeration system100 provides a compact, inexpensive, easily installable and modularsolution for enhancing the efficiency of the cooling systems (e.g.,refrigeration systems and building zone cooling systems) in any type offacility implementing a refrigeration system and an AC system (e.g.,supermarket facilities that are located in relatively warmer climates,etc.). The efficiency of the cooling systems may be enhanced byintegrating the AC cooling loads with the CO₂ refrigeration system in aparallel compression arrangement.

Additionally, the parallel compression arrangement of the AC module withMT compressors 14 provides a more efficient method for controlling CO₂pressure within receiving tank 6. For example, the AC module and/or ACcompressor (e.g., AC compressor 36, 136, or 236) provide a moreefficient use for excess CO₂ vapor in receiving tank 6 than bypassingthe CO₂ vapor through gas bypass valve 8.

Further, the AC module operates in a relatively fail-safe manner in theevent of malfunction or maintenance of the AC compressor. For example,by permitting CO₂ discharge flow from the AC evaporator to re-routethrough gas bypass valve 8 (e.g., via line connection 40 as shown inFIG. 2), the CO₂ refrigerant can be compressed by MT compressors 14.Advantageously, the parallel compression arrangement allows the ACmodule to maintain cooling and pressure regulation functionality in theevent of an AC compressor failure. In some embodiments, the CO₂refrigerant can be rerouted upon a sensed pressure increase in receivingtank 6 when the parallel AC compressor stops.

The AC module provides desired modularity by requiring only a minimumnumber of connection points (e.g., two connection points, threeconnection points, etc.) that are each readily connectable with thepiping (e.g. on or at a “rack” of equipment) for CO₂ refrigerationsystem 100. The AC module also provides desired scalability by allowinga variety of sizes, numbers, and or capacities of evaporators, heatexchangers, and/or compressors within the AC module.

In some embodiments (e.g., as described with reference to FIG. 2), theAC module can be mounted in a refrigeration rack with various componentsof refrigeration system 100 to take advantage of the pressuredifferential between gas cooler/condenser 2 and receiving tank 6. Inother embodiments (e.g., as described with reference to FIGS. 3-4), theAC module can be located remotely in a facility (e.g. nearer the ACloads) and supplied by conventional tubing and components by using thelower-pressure CO₂ liquid supply (e.g., via fluid conduit 7) fromreceiving tank 6. All such embodiments are intended to be within thescope of this disclosure.

In some embodiments, a control system or device provides all thenecessary control capabilities to operate CO₂ refrigeration system 100with and/or without the AC module. The control system or device caninterface with suitable instrumentation associated with the system(e.g., timing devices, pressure sensors, temperature sensors, etc.) andprovide appropriate output signals to operable components (e.g., valves,power supplies, flow diverters, etc.) to control the CO₂ pressure andflow within the system 100. For example, the control system may beconfigured to modulate the position of gas bypass valve 8 to maintainproper CO₂ pressure control within receiving tank 6 as the loading fromthe AC system within the facility changes (e.g. on a daily basis,seasonal basis, etc.).

In some embodiments, the control system or device may regulate, orcontrol the CO₂ refrigerant pressure within gas cooler/condenser 2 byoperating high pressure valve 4. The control system device may operatehigh pressure valve 4 in coordination with gas bypass valve 8 and/orother system components to facilitate improved control functionality andmaintain a proper balance of CO₂ pressures and flows throughout system100 (e.g., to achieve a desired pressure, temperature, flow ratesetpoint, etc.). The control system or device may adaptively control theoperable components of CO₂ refrigeration system 100 and/or AC modules30, 130, and 230 to maintain the desired balance of pressures,temperatures and flow rates notwithstanding variation in systemconditions. Such variation may include variation in refrigeration systemconditions (e.g., refrigeration loads, number or type of MT or LTcompressors, evaporators, expansion valves, etc.), variation in ACmodule conditions (e.g., cooling loads, AC number or type of ACcompressors, evaporators, etc.) and/or variation in other conditions(e.g., the presence or absence of heat exchanger 37, 137, or 237, lengthand diameter of piping, etc.)

According to any exemplary embodiment, the control system or devicecontemplates methods, systems and program products on any non-tangiblemachine-readable media for accomplishing various operations includingthose described herein. The embodiments of the present disclosure may beimplemented using existing computer processors, or by a special purposecomputer processor for an appropriate system, incorporated for this oranother purpose, or by a hardwired system.

Embodiments within the scope of the present disclosure include programproducts comprising machine-readable media for carrying or havingmachine-executable instructions or data structures stored thereon. Suchmachine-readable media can be any available media that can be accessedby a general purpose or special purpose computer or other machine with aprocessor. By way of example, such machine-readable media can compriseRAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any other mediumwhich can be used to carry or store desired program code in the form ofmachine-executable instructions or data structures and which can beaccessed by a general purpose or special purpose computer or othermachine with a processor. Combinations of the above are also includedwithin the scope of machine-readable media. Machine-executableinstructions include, for example, instructions and data which cause ageneral purpose computer, special purpose computer, or special purposeprocessing machines to perform a certain function or group of functions.

As used herein, the terms “approximately,” “about,” “substantially,” andsimilar terms are intended to have a broad meaning in harmony with thecommon and accepted usage by those of ordinary skill in the art to whichthe subject matter of this disclosure pertains. It should be understoodby those of skill in the art who review this disclosure that these termsare intended to allow a description of certain features described andclaimed without restricting the scope of these features to the precisenumerical ranges provided. Accordingly, these terms should beinterpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that the term “exemplary” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

The terms “coupled,” “connected,” and the like as used herein mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent) or moveable (e.g., removableor releasable). Such joining may be achieved with the two members or thetwo members and any additional intermediate members being integrallyformed as a single unitary body with one another or with the two membersor the two members and any additional intermediate members beingattached to one another.

It should be noted that the orientation of various elements may differaccording to other exemplary embodiments, and that such variations areintended to be encompassed by the present disclosure.

It is also important to note that the construction and arrangement ofthe systems and methods for a CO₂ refrigeration system with anintegrated AC module as shown in the various exemplary embodiments isillustrative only. Although only a few embodiments of the presentinventions have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter disclosed herein. Forexample, elements shown as integrally formed may be constructed ofmultiple parts or elements, the position of elements may be reversed orotherwise varied, and the nature or number of discrete elements orpositions may be altered or varied. Accordingly, all such modificationsare intended to be included within the scope of the present invention asdefined in the appended claims.

The order or sequence of any process or method steps may be varied orre-sequenced according to alternative embodiments. Other substitutions,modifications, changes and omissions may be made in the design,operating conditions and arrangement of the various exemplaryembodiments without departing from the scope of the present inventions.

What is claimed is:
 1. An integrated CO₂ refrigeration and airconditioning (AC) system for use in a facility, the integrated systemcomprising: one or more CO₂ compressors configured to discharge a CO₂refrigerant at a higher pressure for circulation through a circuit toprovide cooling to one or more refrigeration loads in the facility; agas cooler/condenser configured to receive the CO₂ refrigerant from theone or more CO₂ compressors; a high pressure valve configured to receivethe CO₂ refrigerant from the gas cooler/condenser via a CO₂ liquid lineconnecting the gas cooler/condenser to the high pressure valve; areceiver configured to receive the CO₂ refrigerant at a lower pressure,the receiver having a CO₂ liquid portion and a CO₂ vapor portion; an ACmodule that provides cooling for a chilled AC coolant different from theCO₂ refrigerant and delivers the chilled AC coolant to AC loads in thefacility, the AC module comprising: an AC evaporator having an inletconfigured to receive CO₂ liquid from the high pressure valve and anoutlet configured to discharge a CO₂ vapor, wherein the AC evaporatorprovides the cooling for the chilled AC coolant by transferring heatfrom the chilled AC coolant to the CO₂ liquid, thereby causing a portionof the CO₂ liquid to evaporate forming the CO₂ vapor; and an ACcompressor arranged in parallel with the one or more CO₂ compressors,the AC compressor configured to receive the CO₂ vapor from the receiver;and a CO₂ vapor line connecting the AC evaporator to the CO₂ vaporportion of the receiver and configured to provide the CO₂ vapordischarged from the AC evaporator to the CO₂ vapor portion of thereceiver; wherein the high pressure valve is controllable to maintain atarget pressure of the CO₂ refrigerant; and wherein the one or morerefrigeration loads are different from the AC loads.
 2. The integratedsystem of claim 1, further comprising: a suction line heat exchangerdisposed between the AC evaporator and the AC compressor, the suctionline heat exchanger configured to receive the higher pressure CO₂refrigerant as a heat source.
 3. The integrated system of claim 2,further comprising: a CO₂ liquid accumulator disposed between thesuction line heat exchanger and the AC compressor.
 4. The integratedsystem of claim 1, further comprising: a control system operable tocontrol an amount of CO₂ vapor directed from the receiver to a suctionof the AC compressor and from the receiver to a suction of the CO₂compressors.
 5. The integrated system of claim 1 wherein the AC moduleis integrated into the CO₂ refrigeration system by three pipingconnections.
 6. An integrated CO₂ refrigeration and air conditioning(AC) system for use in a facility, the integrated system comprising: aCO₂ refrigeration circuit configured to circulate a CO₂ refrigerant torefrigeration loads in the facility, the CO2 refrigeration circuitincluding: a plurality of parallel CO₂ compressors, a gascooler/condenser, a receiver having a CO₂ vapor portion and a CO₂ liquidportion, a high pressure valve positioned downstream of the gascooler/condenser and upstream of the receiver; a CO₂ liquid transportline coupled to the gas cooler/condenser and the high pressure valve,the CO₂ liquid transport line configured to receive CO₂ liquid from thegas cooler/condenser and to provide the CO₂ liquid to the high pressurevalve; a CO₂ liquid supply line coupled to the CO₂ liquid portion of thereceiver and configured to direct CO₂ liquid to one or morerefrigeration loads in the facility; and an AC module that providescooling for a chilled AC coolant different from the CO2 refrigerant anddelivers the chilled AC coolant to AC loads in the facility, the ACmodule comprising: an AC evaporator having an inlet configured toreceive the CO₂ refrigerant from the high pressure valve and an outletconfigured to discharge the CO₂ refrigerant, wherein the AC evaporatorprovides the cooling for the chilled AC coolant by transferring heatfrom the chilled AC coolant to the CO₂ refrigerant, thereby causing aportion of the CO₂ refrigerant to evaporate forming CO₂ vapor; an ACcompressor arranged in parallel with the plurality of parallel CO₂compressors, the AC compressor configured to receive CO₂ vapor from theAC evaporator and from the receiver; and a CO₂ vapor line connecting theAC evaporator to the CO₂ vapor portion of the receiver and configured toprovide the CO₂ vapor from the AC evaporator to the CO₂ vapor portion ofthe receiver; wherein the high pressure valve is controllable tomaintain a target pressure of the CO₂ liquid; and wherein therefrigeration loads are different from the AC loads.
 7. The integratedsystem of claim 6, wherein the AC compressor is configured to at leastpartially regulates a CO₂ pressure within the receiver.
 8. Theintegrated system of claim 6, wherein upon a loss of suction at the ACcompressor, the CO₂ refrigerant is directed through a gas bypass valveto the plurality of parallel CO₂ compressors.
 9. An integrated CO₂refrigeration and air conditioning (AC) system for use in a facility,the integrated system comprising: a CO₂ refrigeration circuit configuredto circulate a CO₂ refrigerant to refrigeration loads in the facility,the CO₂ refrigeration circuit including: a CO₂ compressor configured todischarge the CO₂ refrigerant at a first pressure into a first fluidline, a receiver configured to receive the CO₂ refrigerant at a secondpressure lower than the first pressure, the receiver having a CO₂ liquidportion and a CO₂ vapor portion, and a high pressure valve disposedbetween the CO₂ compressor and the receiver, the high pressure valveconfigured to receive the CO₂ refrigerant at the first pressure from asecond fluid line and discharge the CO₂ refrigerant at the secondpressure; a gas cooler/condenser located upstream of the high pressurevalve and downstream of the CO₂ compressor, the gas cooler/condenserconfigured to receive the CO₂ refrigerant from the first fluid line, thegas cooler/condenser further configured to discharge the CO₂ refrigerantinto the second fluid line; an AC module integrated with the CO₂refrigeration circuit, wherein the AC module provides cooling for achilled AC coolant different from the CO₂ refrigerant and delivers thechilled AC coolant to AC loads in the facility, the AC module including:an AC evaporator configured to receive CO₂ refrigerant from the highpressure valve, wherein the AC evaporator provides the cooling for thechilled AC refrigerant by transferring heat from the chilled AC coolantto the CO₂ refrigerant, thereby causing a portion of the CO₂ refrigerantto evaporate forming CO₂ vapor; an AC compressor arranged in parallelwith the CO₂ compressor, the AC compressor configured to receive CO₂vapor from the CO₂ vapor portion of the receiver and to discharge vaporCO₂ refrigerant into the first fluid line; and a CO₂ vapor lineconnecting the AC evaporator to the CO₂ vapor portion of the receiverand configured to provide the CO₂ vapor from the AC evaporator to theCO₂ vapor portion of the receiver; wherein the high pressure valve iscontrollable to maintain a target pressure of the CO₂ refrigerant; andwherein the refrigeration loads are different from the AC loads.
 10. Theintegrated system of claim 9, wherein the component of the CO₂refrigeration circuit from which the AC evaporator receives CO₂refrigerant is the second fluid line, the system further comprising: afirst CO₂ vapor line fluidly coupling the CO₂ vapor portion of thereceiver to an outlet of the AC evaporator, and a second CO₂ vapor linefluidly coupling the outlet of the AC evaporator to the inlet of the ACcompressor.
 11. The integrated system of claim 9, wherein the componentof the CO₂ refrigeration circuit from which the AC evaporator receivesCO₂ refrigerant is the high pressure valve, wherein the AC evaporator isarranged in an in line configuration to receive an entire mass flow ofthe CO₂ refrigerant from the high pressure valve.